Willam Shewhart
William Shewhart

Walter Shewhart is often called the “Father of Quality Control” – he worked as a process engineer for Western Electric and then at Bell Labs.  He retired in the mid ’50s. Juran actually worked under Shewhart.

We can trace Six Sigma as a measurement standard in product variation back to the 1920s when Walter Shewhart showed that three sigma from the mean is the point where a process requires correction.

Walter A. Shewhart Biography

Walter Andrew Shewhart was an American Physicist and statistician, and he is referred to as the ‘Father of Statistical Quality Control.’ Walter Andrew Shewhart was born to Anton and Esta Barney Shewhart in New Canton, Illinois, in the year 1891. He did his Master’s at the University of Illinois. Later, he attended the University of California at Berkeley to pursue a Ph.D. degree, where he received a Doctorate in physics in 1917. He worked as a professor at both universities. Then, he worked as head of the department of physics at Wisconsin Normal School, Lacrosse.

In 1918, Walter Shewhart worked at the Western Electric Company, one of the largest hardware manufacturers during that time. He assisted engineers in the manufacturing plant in refining the quality of telephone hardware. Later Shewhart went to work at Hawthorne until 1925; then, he worked at the Bell Telephone Research Labs. He would stay there until his retirement.

Walter Shewhart developed modern statistical concepts and scientific methods to minimize human efforts. Shewhart’s methods influenced other statisticians like W Edwards Deming and Joseph Juran. People often refer to these three people – Shewhart, Deming, and Juran – as the three authors of the quality upgrade movements. Shewhart’s work, specifically control charts and the PDSA cycle, influenced the daily work of quality extensively.

Reducing Variation – To Improve Quality

The emphasis on reducing variation to enhance quality is an excellent contribution to quality management. Reducing variation to improve quality resulted in the manufacture of precise things. The concept was applicable in different fields like automobiles, electronics, construction, etc.

Shewhart acknowledged two variation classes, namely ‘special‐cause’ and ‘common‐cause variation. These two categories can also be termed as ‘assignable‐cause’ and ‘chance‐cause’ variations respectively. He designed control charts to explain these two categories of variations. Shewhart proposed new attributes and variables in his control charts. Shewhart proposed to control common-cause to improve quality and reduce scrap. In this way, we can bring any process under statistical control. To distinguish between special cause and common cause variations, we must be sure to meet this criteria. After bringing a process to this state, it would be easy to forecast future outputs and manage processes economically. Shewhart’s principle paved the way for modern scientific analysis of process control.

Economic Incentives

The objective of any industry is to develop economical methods in order to satisfy human needs. We can do this by reducing things to routines requiring little human effort. By using scientific techniques and modern statistical theories, it was possible to set up limits for the results of routine efforts economically. We describe a routine as broken down and no longer economical if the results of any routine process deviate away from the limits. Consequently, we must find the cause of trouble, identify it, and eliminate it in order to make the process economical.

Six Sigma Concept

We use the Greek letter ‘Sigma,’ a Greek letter and mathematical term, to denote standard deviation. It is a standard statistical unit used to measure and describe the distribution of any process about its mean.

Shewhart’s ideas and statistical concepts were embraced in clinical laboratories for several years. Clinical laboratories used these concepts in proficiency testing and quality control operations. Many industries have rediscovered Shewhart’s methods and statistical process control tools, named ‘Six Sigma.’ Recently, Motorola Company has also made use of Six Sigma methods for improving product quality. Motorola Inc. was awarded the Malcolm Baldrige National Quality Award in the manufacturing category for using Six Sigma concepts for quality improvement. In recent times, the Six Sigma concept has acquired public attention extensively. Many other organizations also started using Six Sigma concepts, which has popularized it.

ASQ – American Society for Quality

ASQ of individuals who are passionate about methods of quality control. Members of ASQ contribute to the industry with their ideas of quality control and experience. Shewhart was ASQ’s first honorary associate, and he efficaciously brought together the principles of statistics, economics, and engineering. Individuals working in the field of quality control widely recognize his contributions, particularly because he developed highly effective tools specifically control charts.

Shewhart acquired appreciation in the statistical community for writing Statistical Method from the Viewpoint of Quality Control. Additionally, Bell Laboratories held a number of articles and journals that he had written, but fortunately, they published them later.

Another important element in Shewhart’s achievements was his quality of bringing out ideas and knowledge of other individuals.

Shewhart always believed that statistical theory would serve the needs of industry. After all, he was a man of science who worked patiently to develop ideas that made the world better. Shewhart’s contributions and ideas influenced ASQ intensely. Before his death, Shewhart mentioned to other members of ASQ that he appreciated their contributions. It was their efforts that led to extensive growth in the field of quality control. He also stated that the development, which was beyond his expectations, astonished him.

Comments (8)

There are a lot of misleading articles about the origin of the TQM concepts. You’ve demystified some of my doubts. Thank you!

Should this statement, “Shewhart proposed that to improve quality and reduce scrap, common-cause variation should be controlled,” not be “Shewhart proposed that to improve quality and reduce scrap, special-cause variation should be controlled”?

Hi Matt,

I think your question is really about the difference between common cause variation and special cause variation.

As you standardize a process you’ll have common cause variations. You can then improve those common cause variations.

Special cause variation are those truly unique situations that are by definition difficult to control. You can try to avoid them (eg with checksheets) or mitigate them (eg with a FMEA) – but it’s hard to even tell if your process even has experienced a special cause variation until you’ve standardized the process and brought common cause variation under some kind of control.

Hi Tim ,

I’m finding that I’m getting lost with all the hyperlinks

What is the best way to read through ?

Hi Tehtena,

The hyperlinks are just there in case you don’t understand that topic well and want to dive deeper. If you’re new to the material, I would suggest skipping the hyperlinks and focusing on the core message of the pages.

Best, Ted.

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